Sulfur absorbents

ABSTRACT

A composition and method of making a strength enhanced composition are described. The composition comprises zinc oxide, silica and colloidal oxide solution. The colloidal oxide solution is utilized as a binding agent to provide a strength enhanced absorbent composition that can be utilized in an absorption process for the purpose of removing sulfur contaminants from fluid streams.

[0001] This is a continuation of application Ser. No. 07/826,567 filedon Jan. 27, 1992.

[0002] This invention relates to sulfur-absorbent compositions, themanufacture of sulfur absorbents and their use.

[0003] The removal of sulfur from fluid streams can be desirable ornecessary for a variety of reasons. If the fluid stream is to bereleased as a waste stream, removal of sulfur from the fluid stream canbe necessary to meet the sulfur emission requirements set by various airpollution control authorities. Such requirements are generally in therange of about 10 ppm to 500 ppm of sulfur in the fluid stream. If thefluid stream is to be burned as a fuel, removal of sulfur from the fluidstream can be necessary to prevent environmental pollution. If the fluidstream is to be processed, removal of the sulfur is often necessary toprevent the poisoning of sulfur sensitive catalysts or to satisfy otherprocess requirements.

[0004] Various absorption compositions have been used to remove sulfurfrom fluid streams when the sulfur is present as hydrogen sulfide. Theseabsorption compositions can be manufactured by a variety of methodswhich include, for example, extrusion production techniques. A problemthat is often encountered in the production of these absorptioncompositions is equipment wear caused by the abrasive nature of theabsorption materials being manufactured. In certain attempts to producecommercial quantities of absorbent compositions, excessive equipmentwear and downtime caused by the abrasive characteristics of theabsorption material components have, in effect, rendered the productioncommercially unviable.

[0005] It is desirable for an absorbent composition to not only have ahigh sulfur-absorption capacity but also to have sufficient mechanicalstrength to permit its use as a contact material that is placed as anabsorbent bed within a contact vessel. A low mechanical strength or lowcrush strength of an absorbent agglomerate can lead to excessiveattrition thereby causing undesirable operating difficulties incommercial processes which utilize such absorbent agglomerates.

[0006] A further property of which it is desirable for absorptioncompositions to have is the ability to absorb large quantities ofsulfur. This capability to absorb large amounts and maintain highconcentrations of sulfur is sometimes referred to as “sulfur loading”and is generally reported in terms of percent sulfur loading. The term“percent sulfur loading” is generally defined as the parts by weight ofsulfur absorbed upon the surface or within the pores of an absorptioncomposition per parts by weight of the total absorbent compositionmultiplied by a factor of 100. It is desirable to have an absorptioncomposition with the largest possible sulfur loading capacity.

[0007] An additional property desirable for an absorption composition isthe ability to be regenerated to its original absorbing compositionstate after the absorbing composition has become spent. An absorbingcomposition generally becomes spent when its sulfur loading capacity hasessentially been used up. It is desirable for the absorbing compositionto be able to undergo numerous regeneration cycles without losing itssulfur loading capacity and other desirable properties.

[0008] Even though many absorbing compositions can effectively absorbhydrogen sulfide from fluid streams containing hydrogen sulfide, it isnot uncommon for many of these absorbing compositions to effectivelyoxidize significant amounts of hydrogen sulfide to sulfur dioxide whencontacted with such fluid streams. The resulting sulfur dioxide is notremoved from the fluid stream by the absorbent composition and thuspasses through the absorbent material with the contacted fluid stream.This phenomena is sometimes called “sulfur slippage”. It is desirable tohave an absorption material that has a high capacity to absorb sulfurfrom a fluid stream but which minimizes the amount of sulfur slippage.

[0009] In some absorption compositions, the addition of a promotercompound can be used to allow for easier regeneration of the absorbingmaterial.

[0010] It is, thus, an object of the present invention to provide animproved absorption composition capable of removing certain sulfurcompounds from fluid streams.

[0011] Another object of this invention is to provide an absorptionprocess for the removal of sulfur from fluid streams.

[0012] Yet another object of the present invention is to provide anabsorption composition characterized by exceptional mechanical strengthand an improved process for the production of such composition.

[0013] A still further object of this invention is to provide a methodof manufacturing an absorption composition that minimizes equipment wearand that produces an absorption composition having a high mechanicalstrength.

[0014] In accordance with one aspect of this invention, there isprovided a composition comprising zinc oxide, silica and a colloidaloxide solution. In accordance with another aspect of this invention,there is provided a method for preparing a high crush strengthabsorption composition comprising the step of spraying a colloidal oxidesolution onto a homogeneous mixture comprising zinc oxide and silicaduring tumbling agglomeration to form an agglomerate. Another aspect ofthe present invention includes an absorption process wherein a fluidstream is contacted under absorption conditions with an absorptioncomposition comprising zinc oxide, silica and a colloidal oxidesolution.

[0015] Other objects, advantages and features of this invention willbecome apparent from a study of this disclosure, the appended claims andthe drawings in which:

[0016]FIG. 1 is a schematic process flow diagram illustrating apreferred embodiment of the inventive process for removing sulfurcompounds from contaminated fluid streams; and

[0017]FIG. 2 is a schematic representation of the inventive method forpreparation of an absorption composition illustrating certain featuresof the present invention.

[0018] The composition of matter of the present invention can suitablycomprise, consist of, or consist essentially of, zinc oxide, silica andcolloidal oxide solution. It has been found that an absorptioncomposition having certain exceptional physical properties can beproduced when a colloidal oxide solution is utilized in the productionof the absorption composition or absorption material. In particular, theabsorption composition can have improved mechanical strength, or crushstrength, by the utilization of a colloidal oxide solution when thematerial is manufactured. A further advantage from the utilization of acolloidal oxide solution as a component of the composition of matter ofthis invention is that it permits the use of tumbling agglomerationtechniques in the production of an agglomerate, rather than the use ofextrusion techniques, to agglomerate the material components of thecomposition of matter of this invention. Experience has demonstratedthat the use of silica compounds as a component of absorbentcompositions causes excessive equipment wear when agglomerates areformed by use of extrusion equipment. The excessive equipment wear thatresults from the abrasive characteristics of silica components of theagglomerate materials has rendered the production of such absorbentagglomerates commercially unviable. The use of a colloidal oxidesolution as a binder material in the manufacture of the absorbentcomposition permits the production of the agglomerates by use oftumbling agglomeration techniques, while at the same time, it providesthe unexpected result of producing an agglomerate material that has ahigher crush strength than an agglomerate produced by extrusionagglomeration techniques.

[0019] In another embodiment of this invention, there is provided acomposition suitably comprising, consisting of, or consistingessentially of zinc oxide, silica and colloidal oxide solution whereinthe ratio of zinc oxide to silica in the composition is in the range offrom about 0.25 to 1 (0.25:1) to about 4 to 1 (4:1). Preferably, theratio of zinc oxide to silica in the composition of matter of thisinvention can be in the range of from about 0.5 to 1 (0.5:1) to about1.5 to 1 (1.5:1); but, most preferably, the ratio of zinc oxide tosilica should range from 0.75 to 1 (0.75:1) to 1.25 to 1 (1.25:1).

[0020] The colloidal oxide solution component of the composition ofmatter described herein should be present in an amount which iseffective for providing sufficient binding properties to give a finalagglomerate of the components of the composition of this invention,which has been dried or calcined, or both, having a crush strength of atleast about 3 lbs force (lb_(f)). The final agglomerate can preferablyhave a crush strength in the range of from about 3 lb_(f) to about 6lb_(f); but, most preferably, the crush strength can range from 3.5lb_(f) to 5.5 lb_(f). The term “crush strength” as used herein whenreferring to the mechanical properties of the absorbent agglomerates isthat which is determined by standard ASTM method, D4179-88A, entitled“Standard Test Method For Single Pellet Crush Strength of FormedCatalyst Spheres”. The Standard Test Method ASTM D4179-88A isincorporated herein by reference.

[0021] Alternatively, it is desirable for the amount of colloidal oxidesolution component of the composition of the invention to be such thatthe metal oxide compound content of the composition is in the range offrom an amount effective for providing an agglomerate of saidcomposition having a crush strength at least about 3 lb_(f) to about 30weight percent of the total weight of said composition. Preferably,however, the amount of colloidal oxide solution component of thecomposition of matter of this invention is such that the metal oxidecompound content is in the range of from about 5 weight percent to about20 weight percent; but, most preferably, the metal oxide content shallrange from 5 weight percent to 15 weight percent.

[0022] The composition comprising, consisting of, or consistingessentially of, zinc oxide, silica and colloidal oxide solution canadditionally be dried to form a dried agglomerate or calcined to form acalcined agglomerate or alternatively, both dried and calcined. Thedrying step is used generally to remove the liquid medium of thecolloidal oxide solution from the composition of matter of thisinvention. The drying of the composition can be conducted at anysuitable temperature for removing the liquid medium of the colloidaloxide solution; but, preferably, the drying step should be conducted inthe range of from about 150° F. to about 550° F. More preferably,however, the drying step shall range from about 190° F. to about 480° F.Generally, the time period for such drying shall range from about 0.5hour to about 4 hours, and more preferably, the drying time shall rangefrom about 1 hour to about 3 hours.

[0023] The composition comprising, consisting of, or consistingessentially of, zinc oxide, silica and colloidal oxide solution can becalcined, after undergoing a drying step, to form a calcinedagglomerate. The calcination of the composition or agglomerate can beconducted under any suitable calcination conditions; but, preferably,the composition shall be calcined in the presence of either oxygen or anoxygen-containing fluid at a temperature suitable for achieving thedesired degree of calcination. Generally, the temperature shall rangefrom about 700° F. to about 1400° F.; and, more preferably, thecalcination temperature shall range from about 900° F. to about 1300° F.The calcining step can be conducted for a period of time suitable forachieving the desired degree of calcination, but generally, the time forcalcination shall range from about 0.5 hours to about 4 hours. Mostpreferably, the calcination time shall range from about 1 hour to about3 hours to produce a calcined absorbing composition.

[0024] It can further be desirable to add a Group VIII metal oxidepromoter to the composition comprising, consisting of, or consistingessentially of, zinc oxide, silica and colloidal oxide solution, whichhas previously been either dried or calcined, or both, to produce theaforementioned dried agglomerate or calcined agglomerate. It has beenfound that the addition of certain metal promoters provide certainimproved physical and chemical properties to the absorbent composition.These improved properties include, for example, the ability of thecomposition to hydrogenate sulfur oxide species to hydrogen sulfide andan improved ability of the absorbent composition to easily beregenerated after becoming spent. A further improvement to thecomposition resulting from the addition of metal promoters is in themechanical strength of the composition once it has been promoted andsubsequently dried, or calcined, or both. By incorporating a metal oxidepromoter into the composition of matter described herein followed bydrying and/or calcining the material, the resultant agglomerate willhave an improved mechanical strength or crush strength of at least about5 lbs_(f) Preferably, however, the crush strength of the promotedcomposition shall range from about 6 lbs_(f) to about 14 lbs_(f), andmost preferably, the crush strength shall range from about 7 lbs_(f) toabout 13 lbs_(f).

[0025] An alternative composition of matter of this invention includes acomposition comprising a mixture comprising, consisting of, orconsisting essentially of, zinc oxide, silica and colloidal oxidesolution that has undergone a drying step or a calcining step, or both.The drying of the mixture results in removing from the composition ormixture, the liquid medium of the colloidal oxide solution to therebyform a dried mixture; or in the case where the composition is eitherboth dried and calcined or merely calcined, the calcining of thecomposition or mixture suitably provides a calcined agglomerate. Thedried mixture or the calcined agglomerate can optionally be impregnatedwith a metal oxide promoter for the purposes of improving performance ofthe composition as an absorbent and for improving crush strength of thecomposition by producing a promoted calcined mixture. The metal oxidepromoted composition, having undergone a further calcining step, canhave a crush strength of at least about 5 lbs_(f). Preferably, the crushstrength of the metal oxide promoted absorbent composition, which hasbeen calcined, can range from about 6 lbs_(f) to about 14 lbs_(f), mostpreferably, however, the crush strength shall range from 7 lbs_(f) to 13lbs_(f),

[0026] As for the amount of colloidal oxide solution utilized in themixture comprising, consisting of, or consisting essentially of zincoxide, silica and colloidal solution, it is such that the amount ofmetal oxide compound present in the dried mixture will preferably rangefrom about 1 weight percent to about 30 weight percent of the totalweight of the dried mixture. Preferably, however, the amount ofcolloidal oxide solution utilized in the mixture should be such that themetal oxide content of the dried mixture shall range from about 5 weightpercent to about 20 weight percent. Most preferably, the quantity ofcolloidal oxide solution present in the mixture of this invention willbe such that the amount of metal oxide content in the final driedmixture shall range from 5 weight percent to 15 weight percent.

[0027] The ratio of zinc oxide to silica in the mixture of theabsorption composition can be in the range of from about 0.25 to 1(0.25:1) to about 4 to 1 (4:1). Preferably, the ratio of zinc oxide tosilica in the mixture of the absorption composition can range from about0.5 to 1 (0.5:1) to about 1.5 to 1 (1.5:1); but, most preferably, theratio of zinc oxide to silica in the mixture of the absorptioncomposition can range from 0.75 to 1 (0.75:1) to about 1.25 to 1(1.25:1).

[0028] The silica component of the compositions described herein can beany suitable form of silica, including, but not limited to, naturallyoccurring silica, such as a diatomaceous earth, which is also calledkieselguhr or diatomite or celite, and synthetic silica, such aszeolites, high silica zeolites, precipitated or spray dried silicas orclay and plasma-treated silica or clay. Furthermore, the silica can bein the form of one or more silica compounds that are convertible tosilica under the conditions of absorption composition preparationdescribed herein. Examples of other suitable types of silica that can beused include diatomite, silicate, silica colloid, flame hydrolyzedsilica, hydrolyzed silica, and precipitated silica. Examples of siliconcompounds that are convertible to silica under the production conditionsused in the preparation of the absorption composition described hereininclude, silicic acid, sodium silicate, and ammonium silicate.

[0029] Generally, zinc oxide is the primary active component of thecompositions of the invention, and the zinc oxide will be present in thecompositions in an amount suitable for providing the desired absorptioncapacity. The zinc oxide component of the absorption composition can beeither in the form of zinc oxide or in the form of one or more zinccompounds that are convertible to zinc oxide under the conditions ofpreparation described herein. Examples of such zinc compounds includezinc sulfide, zinc sulfate, zinc hydroxide, zinc carbonate, zincacetate, and zinc nitrate. Preferably, zinc oxide is in the form of apowdered zinc oxide.

[0030] The colloidal oxide solution component of the compositions ofmatter described herein is generally a chemical sol comprising a metaloxide compound or material contained in a solution or a liquid medium.It is preferred that the colloidal oxide solution comprise finelydivided, colloidal-size particles of a metal oxide compound that isuniformly dispersed in a liquid medium. The finely divided particles arenot necessarily in the molecular state, but they are generallypolymolecular particles having a size of which 99 percent of suchparticles will be in the size range of from about 10 angstroms to about10,000 angstroms. It is generally preferred, however, that 99 percent ofthe particles have a size in the range of from about 50 angstroms toabout 10,000 angstroms; and, most preferably, 99 percent of theparticles shall have a size in the range of from 50 angstroms to 5,000angstroms. As for the medium particle size of the colloidal oxidecompounds, it is desirable to have a medium size in the range of fromabout 50 angstroms to about 10,000 angstroms. Preferably, the mediumparticle size should range from about 10 angstroms to about 1000angstroms, and most preferably, the medium particle size can range from100 angstroms to 500 angstroms.

[0031] Typical solid concentrations in a colloidal oxide solution canrange from about 1 weight percent to about 30 weight percent solids,with the weight percent of solids being defined as a fraction of theweight of solids to the total weight of the colloidal oxide solutionmultiplied by a factor of 100. The solution pH can range from about 2 toabout 11 depending upon the method of preparation of the colloidal oxidesolution. It is preferred that the invention use a colloidal oxidesolution comprising a metal oxide selected from the group consisting ofalumina, silica, titania, zirconia, tin oxide, antimony oxide, ceriumoxide, yttrium oxide, copper oxide, iron oxide, manganese oxide,molybdenum oxide, tungsten oxide, chromium oxide and mixtures of any twoor more thereof It is presently preferred that the colloidal oxidesolution be one of either a colloidal alumina solution or a colloidalsilica solution or some mixture thereof. The solvent or liquid medium ispreferably water which serves as an aqueous solvent.

[0032] The compositions described herein can optionally be promoted withany suitable metal oxide promoter. Examples of such suitable metal oxidepromoters include the oxides of manganese, rhenium, copper, molybdenum,tungsten, Group VIII metals of the Periodic Table, and any other metaloxide that is known to have hydrogenation ability of the type necessaryto reduce sulfur oxide species to hydrogen sulfide. Preferably, themetal oxide promoter is a Group VIII metal oxide promoter with the GroupVIII metal being from the group consisting of iron, cobalt, nickel,ruthenium, rhodium, palladium, osmium, iridium and platinum. In the mostpreferred embodiment of the present invention, the absorbing compositionis promoted with nickel oxide.

[0033] The metal oxide promoter can be added to the absorbingcomposition in the form of the elemental metal, metal oxide, and/ormetal-containing compounds that are convertible to metal oxides underthe calcining conditions described herein. Some examples of suchmetal-containing compounds include metal acetates, metal carbonates,metal nitrates, metal sulfates, metal thiocyanates and mixtures of anytwo or more thereof.

[0034] The elemental metal, metal oxide, and/or metal-containingcompounds can be added to the absorbing composition by any method knownin the art. One such method is the impregnation of the absorbingcomposition with a solution, either aqueous or organic, that containsthe elemental metal, metal oxide, and/or metal-containing compounds.After the elemental metal, metal oxide, and/or metal-containingcompounds have been added to the absorbing composition, the promotedcomposition is dried and calcined, as described hereinafter.

[0035] The elemental metal, metal oxide, and/or metal-containingcompounds can be added to the absorbing composition as components of theoriginal mixture, or they can be added after the absorbing compositionhas been dried and calcined. If the metal oxide promoter is added to theabsorbing composition after it has been dried and calcined, then thenow-promoted composition is dried and calcined a second time to form thepromoted absorbing composition. The now-promoted composition ispreferably dried at a temperature in the range of about 150° F. to about570° F., but more preferably, the drying temperature will range from190° F. to 480° F., for a period of time generally in the range of fromabout 0.5 hour to about 8 hours, more preferably in the range of fromabout 1 hours to about 5 hours. The dried, promoted composition is thencalcined in the presence of oxygen or an oxygen-containing inert gasgenerally at a temperature in the range of from about 700° F. to about1400° F., and more preferably in the range of from 930° F. to 1330° F.,until volatile matter is removed and the elemental metal and/or themetal-containing compounds are substantially converted to metal oxides.The time required for this calcining step will generally be in the rangeof from about 0.5 hour to about 4 hours, and will preferably be in therange of from about 1 hour to about 3 hours.

[0036] The metal oxide promoter will generally be present in theabsorbing composition in an amount in the range of from about 0.1 weightpercent to about 15 weight percent, and will more preferably be in therange of from about 2.0 weight percent to about 7.5 weight percent, mostpreferably in the range of from 5 to 7 weight percent.

[0037] Once the absorbent composition components are properly mixed andagglomerated, the mixture can advantageously undergo a drying step forremoving certain quantities of the liquid medium of the colloidal oxidesolution component of the compositions described herein. The drying ofthe agglomerates can be conducted at any suitable temperature forremoving excess quantities of liquid; but preferably, the dryingtemperature will range from about 150° F. to about 550° F. Morepreferably, however, the drying temperature shall range from about 190°F. to about 480° F. Generally, the time period for such drying shallrange from about 0.5 hour to about 8 hours and, more preferably, thedrying time shall range from about 1 hour to about 5 hours. The methodand apparatus used for performing the optional drying step are notcritical aspects of this invention and any suitable methods andapparatuses known in the art can be used. Examples of many of themethods and apparatuses suitable for use in this invention for drying anagglomerate are described at length in Perry's Chemical Engineers'Handbook, pages 20-3 through 20-75 (6th edition, 1984).

[0038] Molybdenum compounds suitable for use as a source for a promotermetal are ammonium molybdate, potassium molybdate, molybdenum oxidessuch as molybdenum (IV) oxide and molybdenum (VI) oxide and the like andmixtures of any two or more thereof.

[0039] Tungsten compounds suitable for use as a source for a promotermetal are ammonium tungstate, potassium tungstate, tungsten oxides suchas tungsten (IV) oxide and tungsten (VI) oxide and the like and mixturesof any two or more thereof.

[0040] Another embodiment of the invention includes a method forpreparing a high crush strength absorption composition which avoids theproblems with excessive equipment wear caused by the abrasive nature ofcertain absorption components, such as silica. This novel methodeliminates the problems with high equipment wear by allowing the use oftumbling agglomeration methods to form agglomerates of the compositionsdescribed herein. The use of tumbling-type or disk-type agglomerators toform agglomerates is well known in the art. Description of methods andapparatuses used for performing such tumbling-type agglomerationprocedures can be found in various art references, such as, for example,Perry's Chemical Engineer's Handbook (6th edition 1984), wherein atpages 8-65 through 8-68 such methods and apparatuses are described atlength. When referred to herein, the term “agglomeration” is thatprocess whereby small particles are gathered together into largerparticles of relatively permanent masses. These permanent masses can beany suitable shape, such as irregular pellets or balls, but tumblingagglomeration methods generally provide substantially spherically shapedagglomerates. While the utilization of tumbling-type agglomerators iswell known in the art, the use of certain binders to assist in theformation of agglomerates and the effects of such binders upon themechanical properties of the final agglomerates are not always generallyknown by those in the art. In particular, a novel aspect of the methodfor preparing high crush strength absorption compositions is the use ofa colloidal oxide solution as a binding agent during tumblingagglomeration of the absorbent components of the compositions describedherein. The art does not teach the use of colloidal oxide solution as asuitable agent for binding the absorbent compounds of zinc oxide andsilica. Furthermore, in addition to the unexpected binding properties ofcolloidal oxide solutions, there is also the result that the finalagglomerates have unexpectedly good mechanical properties.

[0041] In one embodiment of the methods of preparing a high crushstrength absorption composition, a colloidal oxide solution is sprayed,in a spraying step, onto a homogeneous mixture comprising, consistingof, or consisting essentially of, zinc oxide and silica during tumblingagglomeration of the homogeneous mixture to form an agglomerate. Anysuitable method for forming a spray of the colloidal oxide solution canbe used in this invention. The spray can generally be in the form ofsmall droplets or dispersed droplets which serve to wet the homogeneousmixture during tumbling agglomeration so as to permit the formation ofspheres or balls.

[0042] The ratio of zinc oxide to silica in the homogeneous mixture canrange from about 0.25:1 to about 4:1. Preferably, the ratio of zincoxide to silica in the homogeneous mixture can be in the range of from0.5:1 to about 1.5:1; but, most preferably, the ratio can range from0.75:1 to 1.25:1. Additionally, the homogeneous mixture can be a mixturecomprising, consisting of, or consisting essentially of, zinc oxide andsilica in the form of a fine powder. This homogeneous powder mixture cansuitably be agglomerated by spraying of the colloidal oxide solutionupon such homogeneous powder mixture while tumbling the homogeneouspowder mixture within an inclined rotating disk agglomerator, which isequipped with a rim. As earlier mentioned, this tumbling agglomerationresults in the formation of an agglomerate that is substantially in theshape of a sphere.

[0043] The colloidal oxide solution utilized in the method of preparinga high strength absorption composition has the same properties as thecolloidal solution or sol earlier described herein. The amount of thecolloidal oxide solution utilized in the agglomeration of thehomogeneous mixture or the homogeneous powder mixture is to be such toprovide an agglomerate, either in a dry form or a calcined form, havinga content of the metal oxide compound from an amount that is effectivefor providing an agglomerate having a crush strength of at least 3lbs_(f) to about 30 weight percent of the total weight of theagglomerate. Preferably, however, the amount of colloidal oxide solutionutilized in the agglomeration step should be such that the metal oxidecontent of either the dried agglomerate or calcined agglomerate shallrange from about 5 weight percent to about 20 weight percent. Mostpreferably, the quantity of colloidal oxide solution utilized in theagglomeration of the composition will be such that the amount of metaloxide content in either the dried agglomerate or the calcinedagglomerate shall range from 5 weight percent to 15 weight percent.

[0044] As earlier mentioned, the novel method described herein forpreparing a high crush strength absorption composition gives a finalagglomerate, which has been either dried or calcined, or both, having anexceedingly high crush strength of at least 3 lbs_(f). The finalagglomerate can preferably have a crush strength of from about 3 lbs_(f)to about 6 lbs_(f); but preferably, the crush strength can range from3.5 lbs_(f) to 5.5 lbs_(f).

[0045] It has further been discovered that by adding a Group VIII metalcompound promoter to a dry agglomerate prepared by the methods describedherein and subsequently calcining the thus promoted agglomerate, animprovement in the crush strength of an unpromoted calcined agglomeratecan be achieved. This metal oxide promoted agglomerate has substantiallyimproved mechanical properties over that of the unpromoted agglomeratein that such a metal oxide promoted agglomerate, after having undergonea further calcining step, can have a crush strength of at least 5lbs_(f). Preferably, the crush strength of such metal oxide promotedabsorbent composition, which has subsequently been calcined, can rangefrom about 6 lbs_(f) to about 14 lbs_(f); most preferably, however, thecrush strength can range from 7 lbs_(f) to 13 lbs_(f).

[0046] The metal oxide promoters can be added to the agglomeratesproduced by the methods herein by any method known in the art. Onepreferred method for adding a promoter to the agglomerates describedherein is by the impregnation of the agglomerates by a standardincipient wetness procedure, whereby the agglomerates are impregnated byeither an aqueous or an organic solution containing the desirable amountof promoter metal that has been diluted with a volume of the aqueous ororganic solvent that is equal to the total pore volume of the absorbentmaterial or the agglomerate material being impregnated. Suitable metaloxide promoters have been earlier described herein. The amount of metaloxide promoter that can be added to the agglomerate should be such thatthe amount in the final calcined or dried agglomerate is in the range offrom about 0.1 weight percent to about 15 weight percent, and will morepreferably be in the range of from about 2 weight percent to about 7.5weight percent, most preferably, the metal oxide promoters will be inthe range of from 5 to 7 weight percent. The operating conditions fordrying and calcining of the agglomerates has thoroughly been describedhereinabove.

[0047] As an additional embodiment of the present method for preparing ahigh crush strength absorption composition, a homogeneous powder mixtureprepared by mixing zinc oxide and silica with water to form a mixture,undergoes a drying step to form a dried mixture, which subsequently ismilled to form a homogeneous mixture. The milled homogeneous mixture canbe utilized in the methods described hereinabove. Any suitable methodfor mixing the zinc oxide and silica components with water can be used,and it can be done in a batch-wise fashion or a continuous fashion,provided that the components are thoroughly and intimately mixed priorto further processing. Suitable types of batch mixers include, but arenot limited to, change-can mixers, stationary-tank mixers, double-armedkneading mixers, having any suitable agitator or blades, such as sigmablades, dispersion blades, multi-wiping overlap blades, single curveblades, double-nabin blades and the like. Suitable types of continuousmixers can include, but are not limited to, single or double screwextruders, trough-and-screw mixers and pugmills. To achieve the desireddispersion of the materials, they are mixed until a homogeneous mixtureis formed. The mixing time should be sufficient to give a uniformmixture and generally will be less than about 45 minutes. Preferably,the mixing time will be in the range of from about 2 minutes to about 15minutes.

[0048] Following the mixing of water with the absorbent componentscomprising, consisting essentially of, or consisting of, zinc oxide andsilica, the thus-formed mixture is dried to remove the water utilized inthe mixing step. Any suitable method for drying can be used and shouldbe such that a substantially dry mixture is formed. The operatingconditions for the drying step have been earlier described herein.

[0049] The dried mixture of zinc oxide and silica can further be reducedin size preferably to the form of a homogeneous powder mixture by anysuitable or known method of size reduction. There are many known methodsand apparatuses for size reduction and reference is hereby made to theexamples shown and described at length in Perry's Chemical Engineer'sHandbook, (6th edition 1984), pages 8-20 to 8-48. Any of these sizereduction methods and apparatuses can be used for milling purposes andfor the purposes of forming a powder for subsequent use in tumblingagglomeration to form an agglomerate by the aforementioned methods ofspraying a colloidal oxide solution onto such powder.

[0050] The sulfur removal processes of the present invention can becarried out by means of any apparatus whereby there is achieved analternate contact of the absorbing composition with a sulfur-containinggaseous feed stream and, thereafter, of the absorbing composition withoxygen or an oxygen-containing gas which is utilized to regenerate theabsorbing composition. The sulfur removal process is in no way limitedto the use of a particular apparatus. The sulfur removal process of thisinvention can be carried out using a fixed bed of absorbing composition,a fluidized bed of absorbing composition, or a moving bed of absorbingcomposition. Presently preferred embodiment is the use of a fixed bed ofabsorbing composition.

[0051] In order to avoid any casual mixing of the gaseous feed streamcontaining sulfur compounds with the oxygen or oxygen-containing gasutilized in the regeneration step, provision is preferably made forterminating the flow of the gaseous feed stream to the reactor andsubsequently injecting an inert purging fluid such as nitrogen, carbondioxide or steam. Any suitable purge time can be utilized but the purgeshould be continued until all hydrocarbon and/or hydrogen sulfide areremoved. Any suitable flow rate of the purge fluid can be utilized. Apresently preferred purge fluid flow rate is one which will give agaseous hourly space velocity (GHSV) in the range of from about 800 GHSVto about 1200 GHSV. As used herein, the term “gaseous hourly spacevelocity” is defined as the ratio of the gaseous volumetric flow rate,at standard conditions of 60° F. and one atmosphere of pressure, to thereactor volume.

[0052] The composition of matter of this invention can be utilized toremove trace quantities of sulfur compounds from any suitable type ofgaseous feed steam containing contaminating quantities of sulfurcompounds. Such gaseous streams can contain sulfur compounds in theconcentration range upwardly to about 2 mole percent. The sulfurcompounds are generally of the type consisting of hydrogen sulfide,sulfur dioxide, carbonyl sulfide, carbon disulfide, and mixtures of twoor more thereof. One preferred embodiment of the invention includes theprocessing of Claus plant tail gas streams. Of these Claus plant tailgas streams, they can be from either a Claus process operated in a modefor minimizing sulfur dioxide or the tail gas stream can undergo a priorhydrogenation step whereby the sulfur compounds within the tail gasstream are reduced to hydrogen sulfide. The sulfur dioxide minimizationoperating mode of the Claus process is conducted by providing thereaction zone with a slight excess of hydrogen sulfide above thestoichiometric requirement for the Claus reaction. This slightstoichiometric excess of hydrogen sulfide results in minimizing theamount of sulfur dioxide that is present in a Claus tail gas. If theratio of hydrogen sulfide to sulfur dioxide in the reaction zone of aClaus plant approximates 2:1, then the ratio of hydrogen sulfide tosulfur dioxide in the Claus tail gas will also approximate 2:1.Generally, the concentration of sulfur compounds in a Claus tail gasstream will be less than 2 mole percent; the carbon dioxide will bepresent in the tail gas stream at a concentration in the range of fromabout 5 to about 60 mole percent. Water normally will be present in therange of from about 10 mole percent to about 40 mole percent, nitrogenwill be present in the range of from about 20 mole percent to about 50mole percent and hydrogen will be present in the range upwardly to about2 mole percent.

[0053] The gaseous stream containing a concentration of sulfur compoundsis contacted with the novel absorption compositions described herein toproduce a treated effluent stream having a substantially reducedconcentration of sulfur compounds. Preferably, the substantially reducedconcentration of the sulfur compounds in the treated effluent stream canbe less than 0.5 mole percent of the treated effluent stream. Mostpreferably, the substantially reduced concentration of sulfur compoundsin the treated effluent stream can be less than 0.02 mol percent of thetreated effluent stream.

[0054] Any suitable temperature for the sulfur-removal processes of thepresent invention can be utilized which will achieve the desired removalof sulfur from a gaseous feed stream. The temperature will generally bein the range of from about 300° F. to about 1110° F. and will, morepreferably, be in the range of from about 390° F. to about 840° F.

[0055] Any suitable temperature can be utilized which will regeneratethe absorbing composition from its sulfided form back to the originalabsorbing composition form. The regeneration temperature will generallybe in the range of from about 700° F. to about 1500° F. The regenerationtemperature is preferably in the range of from about 800° F. to about1400° F. Most preferably, the regeneration temperature should range fromabout 800° F. to about 1300° F.

[0056] Any suitable pressure can be utilized for the processes of thepresent invention. The pressure of the gaseous feed stream being treatedis not believed to have an important effect on the absorption process ofthe present invention, and will generally be in the range of from aboutatmospheric pressure to about 2,000 psig during the treatment.

[0057] Any suitable residence time for the sulfur-containing gaseousfeed stream in the presence of the absorbing composition of the presentinvention can be utilized. The residence time expressed as volumes ofgas at standard temperature and pressure per volume of absorbingcomposition per hour will generally be in the range of about 10 to about10,000 and will, more preferably, be in the range of about 250 to about2500.

[0058] In the preferred embodiment of the invention, the Claus planteffluent stream having a concentration of sulfur compounds can beintroduced into an absorption zone containing any of the novel absorbentcompositions described herein to remove at least a portion of theconcentration of sulfur compounds to produce a treated effluent streamhaving a substantially reduced concentration of the sulfur compounds toproduce a laden absorbent composition. Periodically, the laden absorbentcomposition can be regenerated by passing an oxygen-containing gas incontact with the laden absorbent composition to produce both aregenerated absorbent and a regeneration effluent stream. Clausprocesses are well known in the art and any references herein to Clausprocesses or Claus plants refers to those conversion processes forrecovering elemental sulfur from fluid streams, sometimes referred to asacid gas streams, containing primarily hydrogen sulfide and carbondioxide. These acid gas streams are generally fluid streams having theirorigin from a main gas treating system used to remove hydrogen sulfideand carbon dioxide from fluid streams containing such. The acid gasstream is charged to the thermal zone of a Claus plant wherein a portionof the hydrogen sulfide is combusted in the presence of air. In thethermal zone of the Claus plant, the hydrogen sulfide will generallyreact with oxygen to form sulfur dioxide and water by the followingreaction equation:

2H₂S+3O₂→2SO₂+2H₂O.

[0059] In order to convert the sulfur compounds contained in the acidgas stream to elemental sulfur, the effluent from the Claus plantthermal zone will pass to a Claus plant sulfur recovery zone or reactionzone wherein the sulfur dioxide is reacted with the unconverted hydrogensulfide to form elemental sulfur and water in accordance with thefollowing equation:

2H₂S+SO₂→3S+2H₂O.

[0060] For the optimum recovery of sulfur from the hydrogen sulfide inthe acid gas stream, it is most desirable to maintain a ratio ofhydrogen sulfide to sulfur dioxide in the fluid stream to the Clausreactor zone of about 2:1. In order to achieve this optimum ratio, theamount of air charged to the Claus plant thermal zone will be controlledso as to react a sufficient amount of HS with oxygen to form thenecessary ratio of SO. The Claus plant effluent stream or tail gas willgenerally have only trace quantities of sulfur compounds which includehydrogen sulfide and sulfur dioxide. Other possible sulfur compoundscontained within the tail gas stream can include carbon disulfide andcarbonyl sulfide. As earlier described, the Claus process can beoperated in a sulfur dioxide minimization mode or, alternatively, thetail gas can further undergo a hydrogenation step whereby sulfurcompounds are reduced to hydrogen sulfide prior to downstreamprocessing. Preferably, the concentration of sulfur compounds can beless than about 2 mole percent of the tail gas stream.

[0061] The Claus plant effluent stream or tail gas stream having aconcentration of sulfur compounds is introduced into a vessel definingan absorption zone containing the novel absorbent composition describedherein. Within the absorption zone, at least a portion of theconcentration of the sulfur compound contained within the tail gasstream is removed to produce a treated effluent stream having asubstantially reduced concentration of the sulfur compounds, but,preferably having a concentration of sulfur compounds of less than about0.5 mol percent and, most preferably, less than about 0.1 mol percent.The removed sulfur compounds will be absorbed upon the surfaces andwithin the pores of the absorbent composition to produce a ladenabsorbent composition. The chemical changes that are believed to occurin the absorption composition during the absorption or removal step aresummarized in the following equation:

ZnO+H₂S→ZnS+H₂O.

[0062] Once the absorbent composition becomes substantially completelysulfided, it is a laden absorbent requiring a regeneration in order torestore the composition to its original form. The regeneration isconducted periodically by terminating the fluid flow to the absorptionzone followed by passing an oxygen-containing gas in contact with theladen absorbent to produce a regenerated absorbent in a regenerationeffluent stream. It is believed that the regeneration step occurs by thefollowing equation:

ZnS+O₂→ZnO+SO_(X).

[0063] The regeneration effluent stream which contains the sulfur oxidecompounds can, optionally, be recycled to be mixed with the acid gasstream being charged to the Claus plant thermal zone. This regenerationeffluent stream is mixed with the acid gas stream prior to introducingthe acid gas stream into the Claus plant thermal zone. The benefit fromrecycling the regeneration effluent stream comes from the ability to usethe sulfur oxide compound as a reactant with the unconverted HS to formelemental sulfur and water in accordance with the above equations.

[0064] Referring now to FIG. 1, there is provided a schematicrepresentation of process 10 for removing sulfur compounds fromcontaminated fluid streams. An acid gas stream having a concentration ofhydrogen sulfide is introduced via conduit 12 to furnace 14, whichdefines a w thermal zone of a Claus plant, wherein at least a portion ofthe hydrogen sulfide of the acid gas stream is combusted with oxygenthat is contained within the air that is introduced into the thermalzone defined by furnace 14 via conduit 16. The resultant product fromthe thermal zone is introduced into reactor 18, which defines a reactorzone of the Claus plant, wherein elemental sulfur is recovered throughconduit 20, and a Claus effluent stream is produced and passes by way ofconduit 22 to heating means or heat exchanger 24. The Claus planteffluent stream is, optionally, heated to a desired temperature and thenpasses by way of conduit 26 to absorber vessels 28 a and 28 b, whichrespectively define two separate absorption zones. Contained within theabsorption zones are any of the novel absorbent compositions describedherein. Within the absorption zones, at least a portion of the sulfurcompounds contained within the Claus plant effluent stream are absorbedby the absorbent composition or removed from the effluent stream toproduce a treated effluent stream which is conveyed from absorber vessel28 a or 28 b, or both, via conduit 30. The treated effluent stream willgenerally have a substantial reduction in the concentration of thesulfur compounds. Preferably, the amount sulfur compounds containedwithin the treated effluent stream will be less than about 0.5 molepercent and, most preferably, the concentration of sulfur compounds inthe treated effluent stream will be less than 0.1 mole percent.

[0065] It is generally desirable to have at least two separateabsorption zones in order to permit the simultaneous regeneration of oneabsorption zone while utilizing another absorption zone for removing orabsorbing sulfur compounds from the Claus plant tail gas stream. Havingat least two absorbent zones permits the periodic regeneration of aladen absorbent composition by passing an oxygen or oxygen-containinggas, such as air, in contact with the ladened absorbent to produce aregenerated absorbent and a regeneration effluent stream. Theoxygen-containing gas is introduced into absorber vessel 28 a or 28 b,or both, via conduit 32. Optionally, disposed within conduit 32 isheating means or heat exchanger 34 which, if desired, permits theheating of the oxygen-containing gas prior to passing the gas into atleast one of the absorption zones. The regeneration effluent streampasses from absorber vessel 28 a or 28 b, or both, through conduit 36 tobe mixed with the incoming acid gas stream passing through conduit 12prior to introducing the thus formed mixture to the thermal zone.

[0066]FIG. 2 is provided to illustrate the use of a typical inclined panor disk type agglomerator used in the method for preparing thecompositions of this invention. As shown in FIG. 1, a feeder device 110is provided so that material can be charged to pan 112 of theagglomerator. Any suitable feeder for charging material can be used.That which is shown in FIG. 2, however, is a belt type conveyor on whichthe agglomerate charge material 114 comprising the absorbent componentsis conveyed and discharged to pan 112 by a moving belt 116. Pan 112comprises a disk 118 that is equipped with a rim 120 attached to theouter perimeter edge of disk 118 so as to form an essentially open-end,cylindrically shaped device. To promote the lifting and cascading of thematerial in pan 112, the inside surface of disk 118 can optionally beprovided with a rough surface by any suitable means including, forexample, expanded metal, abrasive coatings or metallized surfaces. Disk118 can be any suitable diameter necessary for giving the requiredcapacity and can range from less than one foot in diameter to more thantwenty feet in diameter. The depth of pan 112 is set by the height ofrim 120, which can be any suitable height that will promote the desiredagglomeration. Generally, the height of rim 120 will approximate twentypercent of the diameter of disk 118.

[0067] Provided on disk 118 is rotation means 122 which permits therotation of pan 112 about its axis. Rotation means 112 is connected bylinking means 124 for transmitting power from power means 126 torotation means 122. Power means 126 can be any suitable device forimparting the power necessary for rotating pan 112 about its axis andcan include electrical motors of any type, engines of any type orturbines of any type. Preferably, however, power means 126 is anelectrical motor with linking means 124 being any suitable deviceincluding those devices which can permit variable speed control of pan112.

[0068] Pan 112 can be inclined at an angle from the horizontal plane, asdepicted in FIG. 2 and as referred to in FIG. 2 by the Greek lettertheta (θ), in the range of from about 15° to about 75°; but, generally,the angle of inclination will range from about 30° to about 65°. Theagglomerate or pellet size is significantly influenced by the angle ofinclination of pan 112.

[0069] To treat and agglomerate the absorption composition, theabsorbent component materials or agglomerating charge 114 is fed to pan112. As disk 118 is rotated about its axis, the material on disk 118undergoes a tumbling action. A colloidal oxide solution is sprayedthrough nozzle 128 upon the materials while disk 118 is rotating. WhileFIG. 2 illustrates spray nozzle 128 as the means by which the colloidaloxide solution is contacted with the agglomerate material, any suitablemethod known in the art for spraying or contacting a liquid onto the dryagglomerate powder can be used. The agglomerating charge is moistened bythe colloidal oxide solution that assists in the formation of pellets.The tumbling action of the materials within rotating pan 112 causes whatis sometimes referred to as a “snowballing” effect whereby the moistenedmaterial agglomerates as the dampened particles come w into contact withother particles thereby forming spheroids. The colloidal oxide solutionused in this process not only provides moisture, which causes adhesionof the particles by capillary attraction of the particle surfaces, butit also gives the unexpected result of providing a final absorptioncomposition agglomerate having improved mechanical properties.

[0070] There are various operating factors of rotating pan 112 whichaffect the ultimate size of the spheroids formed. Some of theseoperating factors can include, but are not limited to, the rotationalspeed of pan 112, the angle of inclination (θ) of pan 112, the locationand rate of introduction of both liquid feed and solid feed and theratio of the height of rim 120 to the diameter of disk 118. Thesefactors, among others, are to be adjusted to provide the desiredagglomerate or pellet size.

[0071] To more fully illustrate and to assist in understanding theinvention, the following examples are provided.

EXAMPLE I

[0072] This calculated Example I provides calculated ranges for thevarious operating conditions, process flows and stream compositions inthe operation of one embodiment of the herein-described invention. TABLEI Typical Operating Conditions, Flows and Compositions (Calculated)Range Acid Gas Feed Stream (12) Composition (mole percent on dry basis)Hydrogen Sulfide 10-98 Carbon Dioxide  0-90 Carbon Sulfide 0-2Hydrocarbon 0-2 Air Stream 1:1 to 2:1 Ratio of Oxygen-to-HydrogenSulfide preferably 0.5:1 Thermal Zone (14) Operating ConditionsTemperature (° C.)  760-1260 Pressure (psig)  5-30 Reaction Zone (18)Operating Conditions Temperature (C. °) 150-400 Pressure (psig)  5-30Claus Plant Effluent Stream (22) Composition (mole percent) SulfurCompounds less than 2 Water 10-40 Hydrogen 0-2 Nitrogen 20-50 CarbonDioxide  5-60 Total Effluent Stream (30) Composition (mole percent)Sulfur Compounds 0.1-0.5 Regeneration Effluent Stream (36) Composition(mole percent) Sulfur Oxides  5-25 Nitrogen 70-90 Water 1-5

EXAMPLE II

[0073] This Example II describes the method of preparing the absorbentcompositions along with the components of such compositions andpertinent physical property data of the prepared compositions.

[0074] Spheres comprising about 38 weight percent celite silica, about50 weight percent zinc oxide (ZnO) and about 12 weight percent aluminawere prepared as follows. First, ZnO and celite powders were mixed for aperiod of approximately 45 minutes in a sufficient amount of water toform a mixture and then dried at a temperature of about 300° F. for 6 to12 hours. The dried material was broken up to a fine powder in a ballmill. The resulting powder was then sprayed with a colloidal solution ofDispal® 18N4-20 alumina (Vista Chemicals) in a sufficient amount toincorporate about 5.25 weight percent alumina in the resultant mixturewhich was thereafter dried to form a dried powder. A portion of thisdried powder was placed in a Dravo Corporation pelletizing disk orpelletizer for forming an agglomerate. While the pelletizing disk wasbeing rotated, an additional amount of the fine powder was continuouslyfed to the pelletizer using a powder feed and the mixture in the diskwas continuously sprayed with a colloidal solution of Dispal® alumina inwater to effect sphere formation. The amounts of powder feed andcolloidal alumina solution sprayed onto the powder was adjusted to yieldspheres with the composition stated above. The disk angle and itsrevolution was manipulated to yield spheres of desired size.

[0075] The spheres were dried at about 275° F. for about 3 hours andthen calcined at about 1175° F. for about two hours. The dried andcalcined spheres were impregnated by use of an incipient wetness methodwith a sufficient amount of Ni(NO₃)₂·6H₂O dissolved in water to yieldabout 7.5 weight percent nickel oxide in the product. This was followedby another drying and calcination step as described above. The physicalcharacteristics of the material before and after nickel impregnation areshown in Table II. Comparative data are also provided in Table II for acomposition similar to that of the inventive composition but which wasprepared by extrusion methods instead of disk agglomeration methods andwhich such comparative composition did not utilize a colloidal solutionas a binder or binding agent. The data presented in Table II show thatthe spherical product has high mechanical strength while stillmaintaining pore volume and bulk density similar to those of thecomparative composition or material. TABLE II Physical Properties of HSAbsorbents Before Ni Impregnation Bulk Water After Ni Impregnation Cr.Str. Density Pore Volume Cr. Str. (lb_(f)/p) (g/cc) (cc/g) (lb_(f)/p)Control Composition Extrudates: 3 0.78 0.40 8 (50 parts ZnO, 40 partsCelite, 10 parts Al₂O₃, 7.5 parts NiO) Invention Spheres: 3½ mesh 4 0.750.38 13 4-5 mesh 5 0.74 0.43 11 5-14 mesh 4 0.74 0.42 7

EXAMPLE III

[0076] This Example III describes the use of the novel material in aprocess for removing HS from a HS-contaminated fluid stream and makes acomparison between the novel material and a control material when bothare utilized in an HS absorption process.

[0077] The novel absorbent described in Example II above was subjectedto an absorption test in which the absorbent was alternately contactedwith a gaseous stream containing HS mixed with an inert gas until thesulfur loading capacity of the absorbent was reached followed then by aregeneration of the sulfur-loaded absorbent to its original ZnO form bycontacting the absorbent with air. The reactor temperature for thecontacting step was maintained at about 800° F. and the regenerationtemperature was maintained at about 1100° F. The sulfur loading capacityof the absorbent was determined to be reached when hydrogen sulfide wasdetected in the effluent stream; at which point, the sulfided materialwas regenerated in air. The SO₂ concentration was measured at 10 minutesafter the start of the absorption step and at breakthrough (BT). Thetest data for the inventive composition is included in Table III. Theabsorbent of this invention exhibited similar sulfur removal ability tothat of the control material while exhibiting much improved mechanicalstrength as demonstrated in Example II above. Even after 100 absorbingand regeneration cycles, only a minor loss in sulfur removal capacitywas noted. The spherical shape of this product is preferred forcommercial operation for a number of reasons including the improvedpressure drop characteristics that result from the use of sphericalabsorbent masses. TABLE III Hydrogen Sulfide Absorption Test ResultsComposition (weight parts) ZnO/Celite/ Cycle Sulfur Loading SampleAl₂O₃/NO Number 10 min. BT (Wt %) A (Control) 50/40/10/7.5 1 180 60 10.614 13.2 20 950 630 13.1 Invention 50/38/12/7.5 1 30 11.3 2 715 470 12.415 805 530 12.4 20 845 555 12.7 100 470 11.0

[0078] It is understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madeherein without departing from the spirit of this invention.

That which is claimed is:
 1. A composition comprising: zinc oxide,silica, and colloidal oxide solution.
 2. A composition as recited inclaim 1 wherein said colloidal oxide solution comprises finely divided,colloidal-size particles of a metal oxide compound that is uniformlydispersed in a liquid medium.
 3. A composition as recited in claim 2wherein the ratio of zinc oxide to silica is in the range of from about0.25:1 to about 4:1 and wherein the amount of colloidal oxide solutionpresent in said composition is such that the metal oxide compoundcontent of said composition is in the range of from an amount effectivefor providing an agglomerate of said composition having a crush strengthat least about 3 lb_(f) to about 30 weight percent of the total weightof said composition.
 4. A composition as recited in claim 3 wherein saidfinely divided, colloidal-size particles have a medium particle size inthe range of from about 50 angstroms to about 10,000 angstroms andwherein said liquid medium comprises water and wherein the concentrationof said finely divided, colloidal-size particles in said colloidal oxidesolution is in the range of from about 1 weight percent to about 30weight percent.
 5. A composition as recited in claim 4 wherein saidmetal oxide compound is selected from the group consisting of alumina,silica, titania, zirconia, tin oxide, antimony oxide, cesium oxide,yttrium oxide, copper oxide, iron oxide, manganese oxide, molybdenumoxide, tungsten oxide, chromium oxide and mixtures of any two or morethereof.
 6. A composition as recited in claim 5 wherein said compositionis in the form of a dried agglomerate.
 7. A composition as recited inclaim 6 wherein said composition is in the form of a calcinedagglomerate.
 8. A composition as recited in claim 7 further comprising agroup VIII metal oxide promoter.
 9. A composition as recited in claim 8wherein said group VIII metal oxide promoter is present in saidcomposition in the range of from about 0.1 weight percent to about 15weight percent.
 10. A composition as recited in claim 9 wherein saidgroup VIII metal oxide promoter is nickel oxide.
 11. A composition asrecited in claim 10 wherein the crush strength of said composition is atleast about 5 lb_(f).
 12. An absorption composition comprising a mixtureconsisting essentially of zinc oxide, silica, and colloidal oxidesolution, said mixture having been dried to remove the liquid medium ofsaid colloidal oxide solution thereby forming a dried mixture having acrush strength of at least 3 lb_(f) and a sulfur loading capacity of atleast about 11 weight percent.
 13. An absorption composition as recitedin claim 12 wherein said colloidal oxide solution comprises finelydivided, colloidal-size particles of a metal oxide compound selectedfrom the group consisting of alumina, silica, titania, zirconia, tinoxide, antimony oxide, cesium oxide, yttrium oxide, copper oxide, ironoxide, manganese oxide, molybdenum oxide, tungsten oxide, chromium oxideand mixtures of any two or more thereof having a medium particle size inthe range of from about 50 angstroms to about 10,000 angstroms uniformlydispersed in an aqueous solvent.
 14. An absorption composition asrecited in claim 13 wherein the ratio of zinc oxide to silica in saidmixture is in the range of from about 0.25:1 to about 4:1 and whereinthe amount of said metal oxide compound present in said dried mixture ispresent in the range of from about 1 weight percent to about 30 weightpercent of the total weight of said dried mixture.
 15. An absorptioncomposition as recited in claim 14 wherein said dried mixture furtherconsists essentially of a group VIII metal oxide promoter which ispresent in said dried mixture in the range of from about 0.1 weightpercent to about 15 weight percent.
 16. An absorption composition asrecited in claim 15 wherein said group VIII metal oxide promoter isnickel oxide and wherein said dried mixture is further calcined toproduce a promoted calcined mixture having a crush strength of at leastabout 5 lb_(f).
 17. A method for preparing a high crush strengthabsorption composition comprising the step of: spraying a colloidaloxide solution onto a homogeneous mixture comprising zinc oxide andsilica during tumbling agglomeration to form an agglomerate.
 18. Amethod as recited in claim 17 wherein the ratio of zinc oxide to silicain said homogeneous mixture is in the range of from about 0.25:1 toabout 4:1.
 19. A method as recited in claim 18 wherein said colloidaloxide solution comprises finely divided, colloidal-size particles of ametal oxide compound that is uniformly dispersed in a liquid medium. 20.A method as recited in claim 19 wherein said finely divided,colloidal-size particles have a medium particle size in the range offrom about 50 angstroms to about 10,000 angstroms and wherein saidliquid medium comprises water and wherein the concentration of saidfinely divided, colloidal-size particles in said colloidal oxidesolution is in the range of from about 1 weight percent to about 30weight percent.
 21. A method as recited in claim 20 wherein the amountof said colloidal oxide solution utilized in said spraying step is suchto provide said agglomerate with a content of said metal oxide compoundof from an amount effective for providing said agglomerate having acrush strength at least about 3 lb_(f) to about 30 weight percent of thetotal weight of said agglomerate.
 22. A method for preparing a highcrush strength absorption composition comprising: agglomerating ahomogeneous powder mixture comprising zinc oxide and silica by sprayinga colloidal oxide solution upon said homogeneous powder mixture whiletumbling said homogeneous powder mixture within a inclined rotating diskhaving a rim to form an agglomerate substantially in the shape of asphere.
 23. A method as recited in claim 22 further comprising: dryingsaid agglomerate to form a dried agglomerate.
 24. A method as recited inclaim 23 further comprising: calcining said dried agglomerate to form acalcined agglomerate having a crush strength of at least about 3 lb_(f).25. A method as recited in claim 24 wherein the ratio of zinc oxide tosilica in said homogeneous powder mixture is in the range of from about0.25:1 to about 4:1 and wherein the amount of colloidal oxide mixtureutilized is such to provide said calcined agglomerate with a metal oxidecompound content in the range of from about 0.1 weight percent to about30 weight percent of the total weight of said calcined agglomerate. 26.A method as recited in claim 25 further comprising: adding a Group VIIImetal oxide promoter to said dried agglomerate in an amount such as togive a metal oxide compound content in said dried agglomerate in therange of from about 1 weight percent to about 30 5 weight percent togive a promoted agglomerate.
 27. A method as recited in claim 26 furthercomprising: calcining said promoted agglomerate to give a promotedcalcined agglomerate having a crush strength of at least 5 lb_(f).
 28. Amethod for preparing a high crush strength absorption compositioncomprising the steps of: (a) mixing zinc oxide and silica with water toform a mixture; (b) drying said mixture to form a dried mixture; (c)milling said dried mixture to form a powder; (d) spraying said powderwith a colloidal oxide solution during tumbling agglomeration to form anagglomerate; (e) drying said agglomerate to form a dried agglomerate;and (f) calcining said dried agglomerate to form a calcined toagglomerate.
 29. A method as recited in claim 28 wherein saidagglomerate or calcined agglomerate, or both, is substantially in theshape of a sphere.
 30. A method as recited in claim 29 wherein saidcalcined agglomerate has a crush strength of at least about 3 lbs.
 31. Amethod as recited in claim 30 wherein said colloidal oxide solutioncomprises finely divided, colloidal-size particles of a metal oxidecompound selected from the group consisting of alumina, silica, titania,zirconia, tin oxide, antimony oxide, cesium oxide, yttrium oxide, copperoxide, iron oxide, manganese oxide, molybdenum oxide, tungsten oxide,chromium oxide and mixtures of any two or more thereof that is uniformlydispersed in a liquid medium.
 32. A method as recited in claim 31wherein said finely divided, colloidal-size particles have a mediumparticle size in the range of from about 50 angstroms to about 10,000angstroms and wherein said liquid medium is water and wherein theconcentration of said finely divided, colloidal-size particles in saidcolloidal oxide solution is in the range of from about 1 weight percentto about 30 weight percent.
 33. A method as recited in claim 32 whereinthe ratio of zinc oxide to silica utilized in mixing step (a) is in therange of from about 0.25:1 to about 4:1.
 34. A method as recited inclaim 33 wherein the amount of colloidal oxide solution utilized inspraying step (d) is such to provide said calcined agglomerate of step(f) or said dried agglomerate of step (e) with a metal oxide compoundcontent in the range of from about 0.1 weight percent to about 30 weightpercent of the total weight of either said dried agglomerate or saidcalcined agglomerate.
 35. A method as recited in claim 34 wherein thespraying step (d) utilizes an amount of said colloidal oxide solutionthat is effective in producing said calcined agglomerate of step (f)having a crush strength of at least about 3 lbs.
 36. A product preparedby the method of claim
 17. 37. A product prepared by the method of claim18.
 38. A product prepared by the method of claim
 19. 39. A productprepared by the method of claim
 20. 40. A product prepared by the methodof claim
 21. 41. A product prepared by the method of claim
 22. 42. Aproduct prepared by the method of claim
 23. 43. A product prepared bythe method of claim
 24. 44. A product prepared by the method of claim25.
 45. A product prepared by the method of claim
 26. 46. A productprepared by the method of claim
 27. 47. A product prepared by the methodof claim
 28. 48. A product prepared by the method of claim
 29. 49. Aproduct prepared by the method of claim
 30. 50. A product prepared bythe method of claim
 31. 51. A product prepared by the method of claim32.
 52. A product prepared by the method of claim
 33. 53. A productprepared by the method of claim
 34. 54. A product prepared by the methodof claim
 35. 55. A process for absorbing hydrogen sulfide from a fluidstream, said process comprising: (a) mixing zinc oxide and silica toprovide a dry homogeneous mixture; (b) providing said dry homogeneousmixture within a pan of a tumbling agglomerator; (c) spraying acolloidal oxide solution, wherein said colloidal oxide solutioncomprises particles of a metal oxide compound dispersed in a liquidmedium said metal oxide compound comprises colloidal-size particleshaving a median particle size in a range from about 50 angstroms toabout 10,000 angstroms upon said dry homogeneous mixture while rotatingsaid pan to thereby form pellets; (d) drying said pellets to providedried pellets; and (e) contacting said dried pellets with a fluid streamcontaining hydrogen sulfide under conditions suitable for absorbinghydrogen sulfide.
 56. A process for absorbing hydrogen sulfide from afluid stream, said process comprising: (a) mixing zinc oxide and silicato provide a dry homogeneous mixture; (b) providing said dry homogeneousmixture within a pan of a tumbling agglomerator; (c) spraying acolloidal oxide solution, wherein said colloidal oxide solutioncomprises particles of a metal oxide compound dispersed in a liquidmedium said metal oxide compound comprises colloidal-size particleshaving a median particle size in a range from about 50 angstroms toabout 10,000 angstroms upon said dry homogeneous mixture while rotatingsaid pan to thereby form pellets; (d) calcining said dried pellets toprovide calcined pellets; and (e) contacting said calcined pellets witha fluid stream containing hydrogen sulfide under conditions suitable forabsorbing hydrogen sulfide.
 57. A process as recited in claim 55 whereinthe ratio of zinc oxide to silica in said dry homogeneous mixture is inthe range of from about 0.25:1 to about 4:1 and wherein the amount ofcolloidal oxide present in said pellets is such that the metal oxidecontent of said pellets is in the range of from an amount effective forproviding said dried pellets with a crush strength of at least about 3lb_(f) to about 30 weight percent.
 58. A process as recited in claim 56wherein the ratio of zinc oxide to silica in said dry homogeneousmixture is in the range of from about 0.25:1 to about 4:1 and whereinthe amount of colloidal oxide present in said pellets is such that themetal oxide content of said pellets is in the range of from an amounteffective for providing said calcined pellets with a crush strength ofat least about 3 lb_(f) to about 30 weight percent.
 59. A process asrecited in claim 55 wherein said colloidal-size particles in saidcolloidal oxide solution are in the range of from about 1 weight percentto about 30 weight percent.
 60. A process as recited in claim 56 whereinsaid colloidal-size particles in said colloidal oxide solution are inthe range of from about 1 weight percent to about 30 weight percent. 61.A process as recited in claim 59 wherein said metal oxide compound isselected from the group consisting of alumina, silica, titania,zirconia, tin oxide, antimony oxide, cesium oxide, yttrium oxide, copperoxide, iron oxide, manganese oxide, molybdenum oxide, tungsten oxide,chromium oxide and mixtures of any two or more thereof.
 62. A process asrecited in claim 60 wherein said metal oxide compound is selected fromthe group consisting of alumina, silica, titania, zirconia, tin oxide,antimony oxide, cesium oxide, yttrium oxide, copper oxide, iron oxide,manganese oxide, molybdenum oxide, tungsten oxide, chromium oxide andmixtures of any two or more thereof.
 63. A process as recited in claim61 wherein said dried pellets further comprise a Group VIII metal oxide.64. A process as recited in claim 62 wherein said calcined pelletsfurther comprise a Group VIII metal oxide.
 65. A process as recited inclaim 63 wherein said Group VIII metal oxide is present in said driedpellets in the range of from about 0.1 weight percent to about 15 weightpercent.
 66. A process as recited in claim 64 wherein said Group VIIImetal oxide is present in said calcined pellets in the range of fromabout 0.1 weight percent to about 15 weight percent.
 67. A process asrecited in claim 65 wherein said Group VIII metal oxide is nickel oxide.68. A process as recited in claim 66 wherein said Group VIII metal oxideis nickel oxide.
 69. A process as recited in claim 67 wherein the crushstrength of said dried pellets is at least about 5 lb_(f).
 70. A processas recited in claim 68 wherein the crush strength of said calcinedpellets is at least about 5 lb_(f).